Pittsburgh Public Theater’s heartwarming production of the Pulitzer Prize-winning play “Primary Trust” illustrates how far simple acts of kindness and empathy can go in uplifting spirits, and perhaps, changing lives forever, for the better. A quartet of Pittsburgh’s most accomplished performers — Monteze Freeland, Malic Maat, Bria Walker-Rhoze and Sam Turich, the latter two in multiple roles — are so darn likable and engaging in their roles, the play feels like a warm embrace of hope for all of its 90 minutes.